| As a flexible platform with high speed movement, the small unmanned aerialvehicle(UAV) able to complete many diffcult tasks by the use of various auxiliary equipment.Its tremendous value had been reflected.Network video system is an important part ofUAV èit use USB network webcam to capture the high-definition video image,then useCDMA wireless network transfer the compressed high-definition video images data to groundstation to display.In military fields,it can assist the Marine Police to complete the maritimepatrol mission èit also can perform reconnaissance and surveillance and intelligence gatheringon the battlefield.In civilian areas,it can watch over natural disaster and rescue victims watchover forest fires watchover large pastures and urban communities.In previous,mass of video transmission systems are based on the analog video signaltransmission,it’s vulnerable to outside electromagnetic interference.On this papers,this UAVvideo transmission system based on digital signal transmission èit’s less susceptible to outsideinterference,it also can achieve the encryption function.Based on system guideline, twoprojects were designed, the two programs’ hardware platforms include microsoft LifeCamStudio webcam the Cisco RV110W router and Israel CompuLab company’s CM-T3530embedded core board,the CM-T3530is ARM+DSP dual-core architecture.The first programuse single-threaded design approach,the applications run on the ARM,use the opened sourcelibrary of x264to encode the video,this designer is relatively easy to achieve.The secondprogram uses multi-threaded design approach,it has a total of five threads èincluding mainthread control thread video capture thread video encode thread video transmission thread èeach thread is an independent run in parallel,except the video encode thread run on theDSP,other threads run on the ARM,thus the speed of the program improve greatly,thenencode the video, it need a lot of computing,the DSP can encode the video fastly,this canrelease the ARM resources,it will not affect the operation of the flight control procedures.Thisdesigner is more complex,it need to solve the communication problem between the RAM andDSP.On the ground we can use VLC player to display the video and store it. |
